Field of the Invention
This invention relates to methods for detecting the presence or absence of antibodies specific to Campylobacter pylori, and more particularly to the clinical use of novel antigenic compositions for detecting the presence of antibodies to C. pylori and/or for diagnosing certain gastrointestinal disorders.
Peptic ulcer disease, gastritis and other inflammatory gastroduodenal conditions are common maladies throughout the world. Numerous studies have indicated that there is a correlation between the presence of C. pylori infection and affliction with peptic ulcer disease or Type B gastritis (the most common form of gastritis). Hence, determining whether or not C. pylori infection is present in patients complaining of gastrointestinal symptoms can be useful in determining the likelihood that the symptoms derive from gastritis or peptic ulcer.
Most current diagnostic methods for C. pylori infection are costly, difficult to perform in a clinical setting, overly time-consuming and/or unduly invasive and uncomfortable for the patient. For instance, one test involves passage of a tube through the mouth and into the stomach or duodenum for obtaining a biopsy of tissue. Another test involves measuring the increase in carbon dioxide released in the breath of a patient who has consumed a solution containing urea. (C. pylori contain the enzyme urease, which releases carbon dioxide from ingested urea.) Costly instrumentation is required to detect this difference. An analogous test involving carbon 14-labeled urea leads to the production of carbon 14-labeled carbon dioxide that is easier to detect. However, this test is undesirable because it involves exposing the patient to a radioactive isotope.
It is known that persons infected with C. pylori tend to develop antibodies specific to the organism. Prior art methods for detecting these antibodies did not, however, identify specific antigenic compositions capable of providing sufficient practical utility and accuracy for widespread clinical use. Antigens which are not sufficiently unique to substantially assure that only C. pylori-specific antibodies are attracted render the formation of antigen/antibody complex inconclusive as to the presence of antibody to C. pylori. Conversely, antigens which are not common to most C. pylori strains or which do not produce strong immunogenic responses may not bind the C. pylori-specific antibodies of patients infected with certain strains. In such a case, the failure of antigen/antibody complex to form does not necessarily indicate lack of C. pylori infection. In the prior art, adequate sensitivity often coincided with inadequate specificity, and vice-versa. Moreover, where sensitivity is low, practical limits are placed on the degree by which the sample may be diluted. Hence, false positive signals are not as easy to eliminate as would be the case at higher dilution.